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• ffmpeg usage corrupts pointer to filenames

  1er décembre 2014, par user296612

  Say I have 2 files in a folder named ’jack.aac’ and ’jill.aac’, and I run the following script ;

  ls -f -tr *.aac |
  
  while read i; do
  
  echo $i
  
  done

  • I get ’jack.aac’ and ’jill.aac’ printed as expected. If however I include ’ffmpeg -i "$i" -f ffmetadata metadata.txt’ in the while-loop, the second filename to be ’read’ ends up missing a character - ’ack.aac’ (instead of ’jack.aac’) for instance. ffmpeg-usage somehow seems to alter the pointer-to-filenames value. Can anyone tell me how to get around this ?

• Play MPEG-CENC encrypted local file on android

  26 mai 2018, par rd7773

  I need to decrypt and play a cenc-aes-ctr mp4 video on the fly which is locally stored on the device.
  The video was encrypted at server end by using following ffmpeg command and then downloaded to phone :

  ffmpeg -i SampleVideo_1280x720_1mb.mp4 -vcodec copy -acodec copy -encryption_scheme cenc-aes-ctr -encryption_key 76a6c65c5ea762046bd749a2e632ccbb -encryption_kid a7e61c373e219033c21091fa607bf3b8 SampleVideo_1280x720_1mb_encrypted.mp4

  It is successfully getting played with ffmpeg command :

  ffplay SampleVideo_1280x720_1mb_encrypted.mp4 -decryption_key 76a6c65c5ea762046bd749a2e632ccbb

  But I do not want to use ffmpeg in android so I am using libeasy library which creates a local http server to make a stream of offline video and then decrypt it on the fly using Cipher. The Cipher which is provided to the LocalHttpServer for decryption process, needs the initialisation vector (iv) for CTR mode which is not externally available to us.
  From above command it is clear that ffmpeg doesn’t require the IV for encryption or decryption to be passed but i guess internally it uses 8 byte random iv.

  This is how i am creating Cipher to pass to LocalHttpServer :

  final Cipher c = Cipher.getInstance("AES/CTR/NoPadding","BC);
  
  c.init(Cipher.DECRYPT_MODE, new SecretKeySpec(hexStringToBytes("76a6c65c5ea762046bd749a2e632ccbb"), "AES"), new IvParameterSpec(new byte[16]));

  So my question is, what value of iv should i pass in this case to Cipher ? My basic requirement is to play a offline MPEG-CENC encrypted mp4 video stored on device.
  Keeping in mind my very limited knowledge of cryptography, references to any library that provides such implementation with or without any tweaks is welcomed.

• Anomalie #2808 : Message erroné d’erreur d’installation de plugin

  3 août 2012, par nicolas -

  C’était ça, bravo et merci !